BOSTON—After the giddiness of a season-opening sweep of the Boston Red Sox, and starter Bruce Zimmermann’s first major league win, the Orioles were faced with the reality that outfielder Austin Hays was injured once again.

In the midst of a seven-run third inning, Hays, who had a two-run double, left the game with what the Orioles termed “right hamstring discomfort.”

Hays, who had a terrific spring training, has seen three straight years marred by injuries and was hoping that this would be the year he’d play through without major injury.

If the hamstring sends Hays to the injured list, outfielder Ryan McKenna, who is on the taxi squad, could fill in. The Orioles have just 12 position players. When Hays left the game, infielder Pat Valaika pinch-ran and then played left field.

“He’ll come in tomorrow, and we’ll see how he is,” Hyde said. Outfielder DJ Stewart is on the injured list because of a strained hamstring that he hurt on March 5th.

Hays’ injury tempered the Orioles’ 11-3 win over the Boston Red Sox before 4,458 at Fenway Park on Sunday. Their 3-0 start is their best since 2017 when they began 4-0. It was their first three-game sweep in Boston since August 25-27, 2017.

Cedric Mullins had five hits, a career-high, and four in the first four innings, an Oriole first. In the first three games, Mullins is hitting .692 (9-for-13) with a 1.637 OPS. Three of his hits were doubles.

“Guys have been playing with each other for a few years, and everything is just starting to click,” Mullins said.

Anthony Santander had three hits, and Trey Mancini and Rio Ruiz each had two as the Orioles produced 17 hits.

“It was nice to see guys up and down the order contribute, starting off with the top three guys having 10 hits,” Orioles manager Brandon Hyde said. “You’re going to win more games than not when that happens.”

The Orioles haven’t had a home run this season, but it hasn’t mattered because of strong pitching and defense and clutch hitting.

“The bats woke up in a big way early in the game,” Hyde said. “Cedric Mullins set the table for us, all three of these games, making things happen, on base six times today, played great center field defense, doing everything extremely well. We had a lot of guys contribute offensively.”

The Orioles scored three runs in the first on an RBI single by Santander and a two-run double by third baseman Maikel Franco.

In the third, the Orioles scored seven times. Shortstop Freddy Galvis’ bases-loaded walk, Hays’ two-run double, a wild pitch, a two-run double by Mancini and an RBI single by Ryan Mountcastle gave the Orioles a 10-0 lead.

“We were able to put up a huge inning like that, and I know we’re capable of doing that many times over,” Mullins said. “It definitely gives our pitchers some leeway to attack the zone, give them some room to breathe, and that’s exactly what happened today.”

Santander’s RBI single in the ninth scored Mullins and accounted for their 11^th run.

Zimmermann threw only 40 pitches in the first four innings, and 73 in six He allowed J.D. Martinez’s first home run, the first allowed by Orioles pitching this season, among his four hits. He struck out five and walked one and got to pitch with a big lead.

“It makes it a lot easier,” Zimmermann said. “My goal today was to go out and give my team a quality start. I was able to do that, and the win was a cherry on top. To watch the offense come alive like that was very encouraging.”

Zimmermann doesn’t think the team’s 3-0 start is a fluke.

“It’s just a great confidence booster for this team,” Zimmermann said. “I think we’re going to surprise a lot of people this year.”

Zimmermann, who went to many Orioles games growing up in Howard County, had never been to an opener until Friday.

“It was fantastic. It was kind of nice to get that third start because I was able to take in Opening Day, come down from that … It was an absolutely awesome experience to take that in and not have to worry about pitching as much.

“It was a really, really great weekend. I thoroughly enjoyed every minute of it.”

Reliever Cole Sulser threw two scoreless innings, and Rule 5 draft pick Tyler Wells pitched a scoreless ninth in his major league debut.

“I’m so encouraged by our pitching. We really threw the ball well all series,” Hyde said.

Now, the Orioles go to Yankee Stadium for three games beginning Monday night, but with a 3-0 record and a 1.67 ERA.

“It means we got off to a nice start, and we’ve got 159 more to go,” Hyde said.

Odds and ends: Relieft pitcher Shawn Armstrong was moved from the paternity list to the injured list. Armstrong, who was away from the club for the birth of his son, must go through the intake process before he rejoins the club … In the three-game series at Yankee Stadium, Jorge López will face Jordan Montgomery on Monday, Dean Kremer will face Gerrit Cole on Tuesday, and John Means will face Jameson Taillon on Wednesday. All three games are 6:35 p.m. starts.…  In each of Hyde’s three seasons, the Orioles have won their opening series …  Mullins’ five-hit game was the first by an Oriole since Mancini’s on September 24, 2019 against Toronto … The Orioles left 14 runners on base and struck out 15 times.